ANN ARBOR, MI – With a twist of a tap tucked away in a corner of his basement, Matt Grocoff fills a glass of water from a purple pipe.

It’s rainwater collected from his rooftop and channeled through gutters, but it has just passed through three stages of micro-filtration, plus carbon and UV filters.

“It’s literally hyper-filtered and incredibly clear, and while it’s legally not potable, technically,” he says, pausing to take a swig, “it is very potable. So yeah, I would let my family drink that. Anybody.”

The Ann Arbor homeowner has been drinking the water that falls on his roof since installing an elaborate rainwater harvesting system several months ago.

It’s complete with a 5,000-gallon storage tank under his lawn, collecting rain from his spouts before feeding into a five-stage filter system that makes a wall in his basement look a bit like a science lab, with a series of tubes, tanks, gauges and a digital display.

The water is “insanely pure,” Grocoff said, arguing it’s cleaner than the city’s municipal water.

“I’ve had it tested,” he said. “By any scientific standard, it’s potable water. The legal standard is different.”

In municipal water districts, plumbing codes in Michigan don’t allow piping filtered rainwater to a drinking water tap such as a kitchen faucet, but Grocoff says his water is clean enough to do so if ever allowed.

He hopes to someday see a shift toward decentralizing municipal water systems, with more homeowners embracing systems like his.

In the meantime, he has the “test tap” in his basement, from which he can drink and still meet code as long as it’s marked non-potable.

“Just by its nature, being rainwater harvested off of a clean metal roof, it’s not going to have PFAS or estrogen or any of the chemicals that you might find in even the cleanest of municipal systems,” he said.

“You’re still going to have biological contaminants, E. coli or anything that comes from animals on the roof, so all of that still has to be filtered out,” he said. “But the source is cleaner. The rain is one of the cleanest source waters you can get.”

Grocoff still has city water running to his house, which he’s required to use for the shower, bathtub and sinks.

But there are legal uses for the filtered rainwater in his house, in addition to outside irrigation.

“The only place that we’re allowed to use it is in our toilets and in the washing machine,” he said, noting code requires purple pipe for lines carrying the filtered rainwater to mark it as non-potable.

A "do not drink" notice on a toilet in Matt Grocoff's house, since the water comes from his rainwater harvesting system. (Courtesy of Matt Grocoff)

Grocoff hopes the code can be relaxed someday to allow piping it through the whole house.

“We harvest enough water from our roof that we could have all of our water needs met,” he said.

The code the city enforces is adopted by the state, so any changes need to come at the state level, city officials said.

Locally, the city has had no discussions of moving away from a centralized water system anytime in the next century, said city spokesman Robert Kellar.

The city is planning more than $280 million in upgrades to its water system over the next several years, including replacing a large portion of the water treatment plant and aging water mains, and upgrades to handle contaminants such as crypto.

The city draws most of its water from the Huron River to a treatment plant on Sunset Road before sending it out through hundreds of miles of pipes to roughly 125,000 water customers.

Grocoff calls that a “fracture critical” system, where contamination at the source or failure at one point can cause a large portion or even the entire system to fail. As he spoke, the city was dealing with a water main break on a nearby street.

“It’s like one of those Rube Goldberg contraptions where you put a ball on one end and it does some simple task at the end, but it goes through this crazy, really fun mechanism to get there,” he said.

Grocoff, a green renovation and sustainability expert, is the founding principal of THRIVE Collaborative, which is behind a solar-powered development on Platt Road, where plans call for creating a mixed-income neighborhood harvesting its own energy and water.

He’s already proving what’s possible with his own historic home on Seventh Street, with rooftop solar panels providing all his energy needs, geothermal heating and now rainwater harvesting.

Grocoff teamed with students from the BLUElab at the University of Michigan to plan, design and implement his rainwater system, with a goal of elevating the conversation about sustainable, equitable and resilient water systems for the next century. Farmington Hills-based Reynolds Water Conditioning Co. donated equipment.

The goal is to demonstrate that 100 percent of his home’s water needs can be met with captured rainwater and by recycling used household water without the use of chemicals.

“And if you can do it on one house, you can do it on the entire system,” Grocoff said.

Grocoff hopes Ann Arbor can begin a conversation about what its water system could look like in 50 or 100 years with a change in thinking. In addition to systems like his, he suggests a series of rainwater harvesting stations around the city could serve neighborhoods around them.

One need only look to nature to find the best system designs, and they’re not linear grids, Grocoff said.

“Nature relies on complex, adaptive ecosystems that are decentralized,” he said.

Though he has concerns about PFAS and he’s noticed sediment in his tap water recently, getting cleaner water wasn’t his motivation for installing a rainwater harvesting system, Grocoff said.

“I certainly drink out of taps all over the city and everything else. Ann Arbor water is generally safe,” he said.

“That said, that doesn’t take into account the future of our water system. It doesn’t take into account the ecology and what we’re doing to our watershed or sustainable systems — real deep resiliency.”